Sedgwick Museum of Earth Sciences

Research Article| September 01, 1977 Specification of fabric shapes using an eigenvalue method N. H. WOODCOCK N. H. WOODCOCK 1Department of Geology, University of Cambridge, Sedgwick Museum, Downing Street, Cambridge CB2 3EQ, England Search for other works by this author on: GSW Google Scholar Author and Article Information N. H. WOODCOCK 1Department of Geology, University of Cambridge, Sedgwick Museum, Downing Street, Cambridge CB2 3EQ, England Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1977) 88 (9): 1231–1236. https://doi.org/10.1130/0016-7606(1977)88<1231:SOFSUA>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation N. H. WOODCOCK; Specification of fabric shapes using an eigenvalue method. GSA Bulletin 1977;; 88 (9): 1231–1236. doi: https://doi.org/10.1130/0016-7606(1977)88<1231:SOFSUA>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Eigenvalues, derived from the "orientation tensor" method for analyzing directional data, are useful indicators of fabric shape. Three possible methods of graphing these eigenvalues are discussed. These provide a convenient visualization of fabric shapes and strengths. Examples are given of the use of such graphs for representing field data and for tracing progressive deformation of fabrics. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Summary In addition to the well-established extension, compression and transcurrent relative movements between plates of the lithosphere, this paper considers intermediate or oblique relative movements, namely, transtension and transpression. Transtension is already well established in oblique zones of ocean spreading which consist of stepped transform faults. Transpression is a more complex process. The tectonic consequences of a transpression model are outlined and it is suggested that the tectonic style in Caledonian Spitsbergen provides evidence for this transpression regime as an intermediate stage between compression and transcurrence. It is also suggested that transpression should occur generally and may relate the development of transcurrent faults in orogenic belts.

Research Article| August 01, 1971 Alpine Deformation and the Oceanic Areas of the Tethys, Mediterranean, and Atlantic A. GILBERT SMITH A. GILBERT SMITH Department of Geology, Sedgwick Museum, Downing Street, Cambridge, England Search for other works by this author on: GSW Google Scholar Author and Article Information A. GILBERT SMITH Department of Geology, Sedgwick Museum, Downing Street, Cambridge, England Publisher: Geological Society of America Received: 02 Apr 1970 Revision Received: 02 Feb 1971 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1971, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1971) 82 (8): 2039–2070. https://doi.org/10.1130/0016-7606(1971)82[2039:ADATOA]2.0.CO;2 Article history Received: 02 Apr 1970 Revision Received: 02 Feb 1971 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation A. GILBERT SMITH; Alpine Deformation and the Oceanic Areas of the Tethys, Mediterranean, and Atlantic. GSA Bulletin 1971;; 82 (8): 2039–2070. doi: https://doi.org/10.1130/0016-7606(1971)82[2039:ADATOA]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract A preliminary least-squares fit of the 1,000-m contour of the continental fragments around the Mediterranean is presented. It extends the Atlantic reassembly of Bullard and others to the Balearic Islands, Corsica, Sardinia, Italy, Yugoslavia, Greece, and Turkey. Geological and geophysical data suggest that the reconstruction applies to Permo-Triassic time. The large gap between southern Eurasia and the northern and eastern parts of the reassembled fragments shows the probable shape of the Tethyan ocean of this period. During Permo-Triassic time the Mediterranean is thought not to have existed, and therefore it should not be regarded as a remnant of the Tethys.As in several other syntheses, the formation of the Mediterranean, together with that of the Alpine orogenic belts around it, are attributed principally to the relative movements between Africa and Eurasia. Unlike these syntheses, the nature of this motion has been estimated much more precisely by constructing a simple sea-floor spreading model of the central and northern Atlantic Ocean. The model permits the relative movement hypothesis to be tested more rigorously than previously.Available spreading data show that at least three phases of relative movement must have taken place. Relative to Eurasia, the opening model shows the earliest phase consists of an eastward movement of Africa in Lower Jurassic to early Upper Cretaceous time, followed by a westward movement in later Upper Cretaceous to late Eocene time, finally terminating with latest Eocene to present-day northward movement.Anomalous Early Permian and Cretaceous paleomagnetic data, the contrasting age differences between ophiolite-chert sequences in the eastern and western Mediterranean region, and the positions of the Alpine orogenic belts are all shown to be consistent with general features of the reassembly and the opening model. The reassembly and the model also permit a self-consistent plate tectonic interpretation to be made of Lower Jurassic geology, which suggests the existence of a single, irregular plate margin between Africa and Eurasia, whose rotation pole was close to the best-fit pole of Africa and North America on the Atlantic reassembly. It is believed to link such diverse features as central Atlantic opening, sea-floor spreading in Yugoslavia and Albania, transcurrent faulting in the eastern Alps, and compressional features in the Crimea and the Great Caucasus.Although Lower Jurassic geology is consistent with a single irregular plate margin, it is shown that, for the reassembly and opening model adopted, all the larger fragments (Spain, Corsica-Sardinia, Italy, and Yugoslavia-Greece-Turkey) must at times have belonged to a plate or plates independent of Africa and Eurasia.Because the Atlantic spreading pattern has been grossly simplified, and also because verifiable reassemblies of later times cannot yet be made, plate tectonic interpretations of such periods are premature, although partial interpretations are still possible. A possible interpretation is given of a phase of movement of the south Atlas fault and of the relationship of the ophiolite-chert sequences in the Oman Mountains and the Zagros Range of Iran to Atlantic sea-floor spreading.A number of fundamental problems emerge, which include the necessity to postulate different mechanisms for eliminating oceans at compressive plate margins, and the conclusion that present interpretations of structures within orogenic belts provide poor estimates of the relative displacement vectors that have produced them. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The use of ultraviolet and visible diffuse reflectance spectrophotometry as a preliminary technique in the investigation of illuminated manuscripts is discussed. Because ancient manuscripts are amongst the most fragile and precious artworks, characterisation of the materials used in their decoration should be performed using non-invasive analytical methods. Ultraviolet and visible reflectance spectrophotometry with optical fibres (FORS) allows non-invasive identification of several colourants used by ancient illuminators, causing no damage or mechanical stress to the artworks subjected to analysis. Identification is usually based on the comparison of analytical data with a spectral database built from painted areas on parchment, created by preparing paints according to ancient recipes as described in medieval technical treatises. Such database and the spectral features of the colourants analysed are discussed, along with the benefits of extending the spectral range of analysis into the shortwave infrared (to 2500 nm). FORS can be best appreciated as a rapid preliminary tool that offers an overview on the main colourants employed and guides the selection of painted areas of manuscripts on which more selective techniques, such as X-ray fluorescence or Raman spectroscopy, can be employed for a more complete and accurate identification.

Summary Consideration of the arctic configuration of the Caledonides leads to a distinction between eastern and western geosynclinal belts. The western belt , comprising the East Greenland, East Svalbard and southern Barents Sea Caledonides is postulated to continue northwards into the Lomonosov Ridge, whilst the western Spitsbergen Caledonides are thought to have originated as part of the North Greenland geosyncline which is also thought to continue northwards to form the western part of the Lomonosov Ridge. The eastern Caledonian geosynclinal belt comprising the Scandinavian Caledonides appears to swing eastwards to link with the Timan Chain and possibly the Urals. The already postulated (‘Proto-Atlantic’) ocean concept is reviewed in the light of the Arctic Caledonides and named Iapetus . Faunal provincialism suggests that the ocean was in existence up to early Ordovician but had substantially closed by mid Ordovician times. Possible relics of the suture marking the closure of this ocean suggest that it lay to the west of the Arctic Scandinavian Caledonides trending NE to latitude 70° N and thence veered eastwards separating the southern Barents Sea Caledonides from those of Arctic Scandinavia, possibly connecting with the northern Uralian ocean. A previous branch of the ocean may have separated East Svalbard and East Greenland as an ocean-like trough. A further (pre-Arctic) ocean may have existed to the north of the North Greenland–Lomonosov Ridge geosynclines. This is named Pelagus . The closure of these oceanic areas and the deformation of the bordering geosynclines delineates three principal continental plates, namely, Baltic, Greenland and Barents Plates. Their relative dominantly E–W motion up to Silurian times produced compression between the Greenland and both the Baltic and Barents plates but dextral transpression and transcurrence between the latter plates. In Late Silurian to Devonian times an increasing northward component controlled late Caledonian transpression and sinistral transcurrence between the Greenland plate and the combined Baltic and Barents plates.

Synopsis The dinosaurs of the Hateg Basin of Transylvania (late Maastrichtian; western Romania) include Theropoda, Sauropoda, Ornithopoda and Ankylosauria. Of these, one of the most enigmatic taxa is the ornithopod that Franz Baron Nopcsa originally described as Mochlodon suessi and M. robustus in 1902. These two species have come to be regarded as a single species of Rhabdodon, R. robustus, which is distinct from R. priscus from the Late Cretaceous of southern France and northern Spain. This study provides a detailed anatomical revision of the Rhabdodon material that was described originally by Nopcsa during the early decades of the 20th century. It also adds information on material discovered in the Hateg area of Romania since the 1930s. A phylogenetic analysis of basal euornithopods indicates that the non‐hadrosaurid material from Hateg comprises two distinct, but congeneric, species. These two species can be distinguished unambiguously from R. priscus. A new genus Zalmoxes is established for the Romanian ornithopod, comprising Z. robustus comb. nov. (the type‐species of the genus) and Z. shqiperorum sp. nov. Phylogenetic analysis indicates that the two species of Zalmoxes and R. priscus are united in the monophyletic clade Rhabdodontidae (nov.). Rhabdodontidae constitutes the sibling clade to Iguanodontia. R. septimanicus, M. suessi, and the Villeveyrac Rhabdodon also appear to be members of Rhabdodontidae. The evolutionary implications of this phylogenetic analysis include the recognition of a ghost lineage, extending from the most recent common ancestor of Rhabdodontidae and Iguanodontia, which extends for 73 million years. This extraordinarily long ghost lineage duration may reflect considerable gaps in the history of this group or the geographical isolation of Rhabdodontidae in Europe during much of the Cretaceous period. The area of origin of the Rhabdodontidae + Iguanodontia clade may be North America, while the common ancestor of Rhabdodontidae dispersed to Europe, at that time a marine‐dominated region with tectonically‐active terrestrial habitats. Adult individuals of Z. robustus are smaller than either of its two closest relatives, Z. shqiperorum and R. priscus, within the Rhabdodontidae, or with many species of Iguanodontia and, therefore, is considered a possible paedomorphic dwarf.

Abstract Isolated specimens of the appendage Anomalocaris canadensis have long been known; a single incomplete specimen of an animal having a pair of these appendages attached anteriorly is described. Seven dorsoventrally compressed, partly complete individuals of a similar animal that had a different pair of appendages (‘F’ of Briggs 1979) attached anteriorly are described, together with two obliquely compressed individuals that are thought to be conspecific. Surrounding the mouth of this latter species is a circlet of plates identical with the supposed medusoid coelenterate Peytoia nathorsti; this species is referred to Anomalocaris; Laggania is a junior synonym. As now understood, Anomalocaris was an animal that reached a length of 0.5 m, the elongate body having a head region bearing one pair of large, lateral eye lobes, each borne on a short stalk, the single pair of appendages attached at the ventral, anterior margin. The 13 segments of the appendage in A. canadensis bore paired spines on the inner side, short spines on the outer side, and there was a terminal, spinose 14th segment. The appendage in A. nathorsti consisted of 11 segments, the 2nd to 10th bearing on the inner side a graduated series of spinose blades, and spines on the lateral and outer sides, the terminal 11th segment ending in a group of spines. The circlet of plates surrounding the mouth was situated ventrally on the head region immediately behind the appendages; the plates bore teeth and the circlet constituted a jaw mechanism; additional groups of spines were present in the buccal cavity. Beneath the head region, behind the mouth, were three pairs of semicircular flaps, strongly overlapping: on the tapering trunk were 11 pairs of triangular lateral lobes, widest at the mid-length of the trunk, reduced progressively in size backward. These lobes were strongly overlapping in the same sense as the flaps on the head, and attached low on the sides. The trunk termination was short and blunt, without any projecting spine or lobe. Attached to the side of the body, above each flap and lateral lobe, was a multi-lamellar structure, apparently a gill. A thin cuticle covered the head region dorsally, and ventrally around the appendages and jaw circlet, behind this becoming a lateral strip that narrowed backward. It is suggested that a thin cuticle covered the trunk region dorsally and hung down beside the gills; this covering may have been continuous, but possibly was divided into tergites. Irregular patches of apatite, and some matrix, occur in the trace of the alimentary canal, which extended to the tip of the trunk. Mineralized patches occur in association with the gills, and as transverse strips, presumed traces of some internal organ or structure. The cuticle of the appendages and jaw circlet was presumably stout, hence these parts of the body were more resistant to decay and so were preserved in isolation. The thin cuticle of the lateral lobes shows rays which were presumably thicker and strengthening in function. We suggest that this animal, the largest known from Cambrian rocks, swam by using the series of closely spaced lateral lobes essentially as a lateral fin along which waves of motion were propagated. If the waves were moved in either the same, or opposite, sense on each side, considerable manoeuvrability would have resulted. The anterior pair of appendages, and jaw mechanism, would have made Anomalocaris a formidable predator, particularly on soft-bodied benthos including the abundant arthropods without a mineralized exoskeleton. No fragments of hard parts have been observed in the gut, but there is evidence that it may have inflicted wounds on trilobites. Anomalocaris was a metameric animal, and had one pair of jointed appendages and a unique circlet of jaw plates. We do not consider it an arthropod, but the representative of a hitherto unknown phylum. It is best known from A. nathorsti, the single specimen of A. canadensis having a different appendage but the rest of the body similar, probably including the jaw circlet. The evidence is insufficient to reach any conclusion on whether or not these two 'species' may be sexual dimorphs of a single species. The single specimen of Amiella ornata is redescribed. It shows what may be lateral lobes like those of Anomalcris, but other features unlike it. We conclude that this specimen is not an example of Sidneyia inexpectans, and is too incomplete for its relationship to be determined.

Tissue-thin parchment made it possible to produce the first pocket Bibles: Thousands were made in the 13th century. The source of this parchment, often called "uterine vellum," has been a long-standing controversy in codicology. Use of the Latin term abortivum in many sources has led some scholars to suggest that the skin of fetal calves or sheep was used. Others have argued that it would not be possible to sustain herds if so many pocket Bibles were produced from fetal skins, arguing instead for unexpected alternatives, such as rabbit. Here, we report a simple and objective technique using standard conservation treatments to identify the animal origin of parchment. The noninvasive method is a variant on zooarchaeology by mass spectrometry (ZooMS) peptide mass fingerprinting but extracts protein from the parchment surface by using an electrostatic charge generated by gentle rubbing of a PVC eraser on the membrane surface. Using this method, we analyzed 72 pocket Bibles originating in France, England, and Italy and 293 additional parchment samples that bracket this period. We found no evidence for the use of unexpected animals; however, we did identify the use of more than one mammal species in a single manuscript, consistent with the local availability of hides. These results suggest that ultrafine vellum does not necessarily derive from the use of abortive or newborn animals with ultrathin hides, but could equally well reflect a production process that allowed the skins of maturing animals of several species to be rendered into vellum of equal quality and fineness.

Abstract 697 taxa of planktonic graptolites are recorded, and their stratigraphical ranges are given, through 60 biozones and subzones in the Ordovician and Silurian strata of England, Wales and Scotland, in the first such stratigraphical compilation for Great Britain since the synthesis of Elles &amp; Wood (1901–1918).

Abstract Lists of families and genera of trilobites from the stratigraphical series of the Ordovician have been compiled, using information considered adequate from various areas in the world. Dissimilarities between these faunas have been assessed at both generic and family level, using Simpson’s index. These indices have been analysed by a non-metric multidimensional scaling technique, and the groupings revealed are interpreted as indicating faunal provinces. Four provinces are recognized in the Lower Ordovician, the faunal characteristics and geographical extent of three of them (the Bathyurid, Asaphid and Selenopeltis provinces) being as previously described. A fourth province, here named the Asaphopsis province, is proposed for South American and Australian faunas in the Arenig and Llanvirn; the affinities of faunas from southeast Asia are indeterminate. In the Caradoc, faunas from areas occupied earlier by Bathyurid, Asaphid and Asaphopsis faunas, together with trilobites from south-east Asia, constitute a single province, here named the Remopleuridid. The Selenopeltis province persists in southern Europe and North Africa. These two provinces are recognizable only by a generic analysis in the Ashgill, and the latest faunas of that series are world-wide. It is assumed that a faunal province originally extended over parts of a single continental mass (cf. Wilson 1966), and that migration between provinces is inhibited by width of seas or temperature differences. An assemblage of continental masses consistent with these assumptions, and with palaeomagnetic data, is proposed to give four palaeogeographical maps for the Ordovician period. The position of the proto-Atlantic ocean proposed by Wilson (1966), and Gondwanaland of McElhinney &amp; Luck (1970), are accepted; the remainder of Eurasia is divided into four blocks. The maps suggest relative movements between continental blocks that may have removed barriers to migration and resulted in progressive merging of the faunal provinces. They are models to be tested against distributions of other animal groups, new palaeomagnetic and palaeoclimatic evidence, and theories on lithosphere plates. The geographical reconstructions imply that the faunas of South America, southern Europe and North Africa inhabited cool waters, those of North America, northern Europe, north-east Asia, south-east Asia and Australia, warm waters. Cooler water faunas appear to have been less diverse. Decreasing provinciality of faunas during the Ordovician appears to have been accompanied by a reduction in total diversity; supposed climatic deterioration does not seem to have resulted in increased diversity. The differences between contemporaneous faunas within the Bathyurid and Remopleuridid provinces are investigated, and are shown to reflect differences in environment and evolution and diversification of groups of trilobites which took place in these environments.

Summary A review of the radiometric evidence suggests that the top of the Devonian should be dated at about 345 m.y. and the base of the system at about 395 m.y. Using cumulative thickness methods the age of the base of the Upper Devonian is estimated at 358 m.y. and that of the base of the Middle Devonian at 370 m.y. Famennian ammonoid species zones must each represent about a million years. Suggestions are made as to where future radiometric work of importance to the time-scale might be undertaken.

Abstract A revised Stratigraphical scheme based on numerous measured sections and extensive mapping is proposed for the Carboniferous and Permian sequences of Spitsbergen and Bjørnøya, the important Arctic archipelago, in order to provide an up-to-date framework for future work there. New data on the fusulinid zones is summarized and the age of the sequence discussed. A brief Stratigraphical interpretation with four maps showing outcrops, thicknesses, active faults, and main lithological boundaries is given and recent published and unpublished work is reviewed.

Abstract Fifteen specimens of A.pedunculata have been prepared, photographed, and drawn to show how each specimen is interpreted and how portions preserved only in part or counterpart are related to the whole. The body was elongate, sub-cylindrical, bearing one pair of conical, branched anterior appendages inserted in the lateral wall, and ten pairs of short, uniramous limbs; anteriorly no distinct head region, posteriorly the body merged into the bases of the last pair of limbs. The cuticle was unmineralized, flexible, the body wall, anterior appendage and limbs, annulated. On the trunk the evenly spaced annulations were high, sharp-crested dorsally, changing to low and rounded laterally and faint or absent ventrally; dorsally the annulations appear to have borne a row of seven tubercles, each tubercle sharp and possibly spinose apically. One annulation opposite midline of anterior appendage and limbs 1-9, three in the space intervening between these limbs, five between anterior appendage and first limb; posteriorly annulations of trunk formed a continuous series with those of last pair of limbs. This arrangement implies that the body consisted of at least 12 somites. Annulations of the anterior appendage were sharp-crested, uniform in height; branches of the appendage were long, slim, pointed, three at the tip and three along the anterior side, each branch slightly flexible and movable about its base. About ten annulations on each limb, uniform in height, the cross-section varied from low, rounded, to high, sharp-crested, as the limb was extended, contracted or flexed. The tip of the limb was bluntly rounded, on the posterior wall of limbs 1-8, and the anterior wall of limbs 9, 10, was a group of seven curved claws. On limbs 2-8 a forwardly directed spine on the seventh annulation and a shorter spine on the distal annulation, on limbs 9 and 10 a prominent, backwardly directed spine. In front of the anterior appendage the one or two annulations were faint, the anterior end of the body bluntly rounded, the mouth, surrounded by a ring of six or so slim papillae, situated medially on the anterior wall. The alimentary canal is not preserved as a sediment fill, but as a reflective strip, widest adjacent to the mouth, extending back to end between the bases of the last pair of limbs. Sagittal length 1 to 6 cm, smallest similar to largest specimen. Aysheaia pedunculata is one of the rarer animals in the Burgess Shale, occurring in association with arthropods and worms, and to an exceptional extent with sponge fragments. It was not a burrowing, mud-ingesting animal, and the soft body would seemingly make it vulnerable to predatory arthropods. It may have been protected by living amid sponge colonies, the claws having facilitated clinging to the sponge, the anterior appendage holding the suctorial mouth in position to feed on the soft parts. While it shows resemblances to both Onychophora and Tardigrada, it is not placed in either group, nor in any taxon of higher rank than Family Aysheaiidae. It may be regarded as the sole known example of the types of lobopod animals from which the arthropod phylum Uniramia, and the Tardigrada, may have been derived.

An abstract is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.

Abstract The Burgess Shale (Middle Cambrian) polychaetes Canadia spinosa Walcott, Burgessochaeta setigera (Walcott) gen. nov. and Peronochaeta dubia (Walcott) gen. nov. are redescribed on the basis of Walcott’s type specimens and on much additional material. Two new polychaetes Insolicorypha psygma gen. et sp. nov. and Stephenoscolex argutus gen. et sp. nov. are described. A poorly preserved specimen of unknown generic affinity is described as type A. The polychaetes are preserved as thin films that adhere to both sides of the split in the rock so that part and counterpart may be available. In C. spinosa, B. setigera and I. psygma, parts of the bodies such as the fascicles of setae are separated by thin layers of sediment that apparently seeped in during turbulent transport in turbidites or mudflows. The bodies therefore lie on two or more planes of microbedding and the factors that control exposure across a specimen are discussed. Aspects of the palaeoecology of the Burgess Shale are reviewed, including the distance the biota was transported prior to burial, the reasons for the exquisite preservation, and the effects of sedimentary compaction. C. spinosa was characterized by broad notosetae that extended across the dorsum, and large fascicles of neurosetae. Lobate branchiae were situated in the inter-ramal spaces. The prostomium bore a pair of elongate tentacles and the straight gut had an eversible unarmed proboscis. Several lines of evidence suggest that C. spinosa was an active benthonic swimmer. B. setigera was peculiar in possessing identical notosetae and neurosetae along the entire body. Long anterior tentacles, possibly of peristomial origin, may have been used in feeding. Indirect evidence indicates that B. setigera inhabited a burrow which it might have excavated with its proboscis. P. dubia may also have burrowed but it had uniramous parapodia bearing simple and acicular setae. The prostomium bore a pair of short appendages. I. psygma had extended neuropodia bearing cirri and elongate setae. The notopodia were reduced and cirri appear to have been wanting. The peculiar prostomium carried a pair of appendages. I. psygma is regarded as a pelagic polychaete. S. argutus possessed uniramous parapodia with simple stout setae. The bilobed prostomium bore at least one pair, and perhaps three pairs, of short appendages. Type A was the largest of the Burgess Shale polychaetes and had prominent setae on at least the anterior section of the body. Type A was a sediment eater but the feeding habits of the other polychaetes are uncertain. Particular attention is given to the influence of decay on the Burgess Shale polychaetes. To place the Burgess Shale polychaetes in some geological perspective other Cambrian worms, including a polychaete from the Spence Shale of Utah, are briefly redescribed and the late Precambrian (Ediacarian) worms Dickinsonia, Spriggina and Marywadea are assessed. Contrary to the findings of other workers, no convincing evidence for placing these latter worms in the polychaetes is forthcoming.

Abstract A detailed description and reconstruction of Canadaspis perfecta demonstrates its status as the earliest well-preserved crustacean. The cephalon consisted of five somites (in addition to the eyes), the thorax eight, and the abdomen seven, excluding the telson. Two pairs of apparently uniramous antennae flanked a median cephalic spine. The mandible bore a massive incisor process posterior of a molar area made up of finer spines, and apparently lacked a palp. The first and second maxillae were essentially similar to the eight pairs of thoracopods, with a multisegmented inner ramus, and foliaceous outer ramus made up of wide filaments attached to a proximal lobe. A bivalved carapace covered the thorax; no rostral plate was present. The abdomen lacked appendages, apart from a pair of spinose ventral projections of the pre-telson somite. There was no caudal furca. The evidence suggests that C. perfecta fed on coarse particles, possibly with the aid of currents set up by the biramous appendages. The erection of a new order Canadaspidida and family Canadaspididae Novozhilov (in Orlov 1960) to include Canadaspis is vindicated, and they are re-defined and the subclass Phyllocarida amended to include them.

Abstract The main feature of the gravity field of Devon and Cornwall is a belt of large negative Bouguer anomalies which follows the line of the granite outcrops. These low anomalies are shown to originate from a shallow structure and are interpreted as being caused by the relatively low density of the granite itself. They indicate that the exposed granites are cupolas on a single elongated batholith which reaches a depth of at least 8 and possibly 20 km. The magnetic anomalies between Dartmoor and Bodmin Moor support the idea of interconnexion. A more detailed interpretation of the gravity anomalies shows that the contacts between the granite and the enveloping country rocks generally slope outwards. For Dartmoor, at least, the base of the batholith seems to be deeper in the south. A mechanism of emplacement combining forcible intrusion with stoping, in which the magma rose in the south, is consistent with the shape suggested. In marked contrast to the granites of the mainland and Scilly Isles there is only a small drop in the Bouguer anomalies over the Lundy granite, suggesting a laccolithic space form. The present high ground corresponding with the granite exposures of the mainland is shown to be isostatically compensated, or even overcompensated, by mass deficiencies implied by the negative anomalies. As the anomalies seem to be caused by the low density of the granite the compensation is almost certainly caused by the relatively low density of the batholith itself. The distribution of the compensating mass deficiency thus suggested is in closest agreement with Pratt’s hypothesis. The depth of compensation is unusually low at about 1 o or 15 km. There is a marked southward increase of the Bouguer anomalies over the Start and Lizard peninsulas which is thought to be related to the presence of a thrust affecting these regions. Similarly, the northward decrease of the gravity anomalies across Exmoor is attributed to a major overthrust beneath which a great thickness of Carboniferous and Devonian rocks is likely to be present. It is thus possible that Coal Measures are to be found at no great depth beneath the Devonian rocks of the Dunster-Minehead region. Over the Culm synclinorium three east-west ridges of higher Bouguer anomalies are superimposed on a westerly regional gradient and are shown to be of shallow origin. The high magnetic anomalies in this area suggest the presence of magnetic rocks extending to a considerable depth. A smaller gravity ‘low’ coincides with the Crediton trough of Permo—Triassic rocks. A detailed traverse at North Tawton indicates that the trough here is V-shaped and has a maximum depth of 340 m. Depth estimates have also been obtained for the Tertiary lacustrine deposits of Bovey Tracey and at Petrockstow.

Abstract Much modern work on graptolite sequences in the British Isles has provided considerably greater detail regarding species occurrence and range than was available to Elles and Wood (1901‐18) and requires that the more refined zonal schemes of, for example, Rickards (1967, 1969, 1970) and Toghill (1968a) should be more fully discussed than was possible in Strachan (1971), Cocks et al. (1971), or Ziegler et al. (1974). The zonal scheme favoured by the writer is discussed zone by zone, and reference is made to the various difficulties which may obtain, to other zonal schemes in use, and to the questions of local, national and international usage. A summary range chart of British Silurian graptoloids is included as Table I.

The settling velocities of empty tests of planktonic foraminifera have been determined experimentally, using tests both from sediment samples and from combusted plankton samples. The modal settling velocity of the species studied was equivalent to that of a quartz sphere of diameter approximately 2.4 times less than the maximum diameter of the foraminifera. Large variations from this mode occur and result from varying test shapes and wall thicknesses. The sequence of foraminifera in graded beds corresponds closely to their settling behavior determined experimentally. The significance of this new information for the production, dissolution, and redistribution of foraminiferal tests is considered briefly.

The holotype of the Mongolian species of ornithopod dinosaur Iguanodon orientalis from the Early Cretaceous (Barremian-Aptian of Khamarin Khural) has been shown to have been established on holotype material that is non-diagnostic, but appears to be closely similar osteologically to the Western European species I. bernissartensis.Additional material collected from the locality known as Khuren Dukh (Dornogov′, Mongolia), which had previously been referred to I. orientalis has been re-examined and shown to represent a new genus and species (Altirhinus kurzanovi gen.et sp.nov) of ornithopod dinosaur from the Early Cretaceous (Late Aptian/Early Albian).The anatomy of this new ornithopod is described; it shows a number of similarities to the known species of Iguanodon, but also demonstrates features which are in some instances unique to this taxon, while others seem to be either convergent upon, or transformational with respect to, the more derived hadrosaurid ornithopods of the Late Cretaceous.Palaeogeographic evidence is corroborative in that it suggests contemporaneous, albeit episodic, links between the Northern Hemisphere landmasses during the Barremian-Albian interval; these explain the appearance of very 'European' large ornithopods (Iguanodon) in Asia in Barremian/Aptian times as a consequence of land-based dispersal.Subsequent isolation of Asia from the European 'domain' during the late Early Cretaceous (Albian) may be responsible for the appearance of derived forms such as Altirhinus, and is suggestive of an Asian centre of origin for the family Hadrosauridae in middle Cretaceous times; this contradicts an earlier vicariance-biogeographic model of ornithopod evolution.The cranial anatomical modifications seen in this new taxon: vertical expansion of the dorsal nasal cavity, lateral expansion and lowering of the cropping beak relative to the jaw line, increase in the number of replacement teeth (but no significant miniaturization of the crowns) and the trend toward formation of a more integrated battery of cheek teeth, seen to varying degrees in several mid-Cretaceous ornithopods are commented upon; they can be interpreted within the context of an evolutionary trend culminating in the cranial complexity seen in the terminal lineage of ornithopods represented by the Late Cretaceous Hadrosauridae.Functionally, some of these changes can be correlated with what can be interpreted as 'improvements' to the efficiency of food gathering and processing which might represent increased niche partitioning and/or responses to increasingly tough and abrasive (xeric adapted) foliage; others, notably the modifications to the nasal cavity (perhaps associated with providing space for a countercurrent moisture conserving turbinal system), are suggestive of a biological response to increasingly seasonal/xeric conditions in the middle of the Cretaceous Period or changes in the floral composition of these times.